A rotary electromotor, particularly a permanent magnet synchronous electromotor, which is small in size and highly efficient, is suitable for use in household electrical appliances, industries, and automotive vehicles, and its range of usage or application in these fields is widening.
To respond to the recent demand for space saving in apparatuses in these fields, miniaturization of the electromotor is essentially required. In miniaturizing the electromotor with its output kept substantially the same, a heat issue occurs.
A heat radiation area, or an area from which generated heat is radiated, of a miniaturized high-power electromotor is relatively small for the amount of the generated heat. Thus, the internal temperature of the electromotor in use becomes high to adversely affect the properties of the electromotor. Namely, there are caused problems such as rise in winding resistance and thermal demagnetization of the permanent magnet.
With the above background, various designs have been considered to enable excellent heat radiation performance in a miniaturized high-power electromotor.
Among the known techniques to enhance the radiation performance are included those disclosed in JP-A-2007-236045 and JP-A-Hei 8-149756.
According to JP-A-2007-236045, a layer or member of a highly-flexible heat-conductive material that is interposed between a stator and a stator frame of an electromotor enhances the radiation performance of the electromotor.
According to JP-A-Hei 8-149756, an electromotor is produced such that a metal film is formed between its stator and stator frame, and an irregular space between the stator and stator frame, which is derived from lamination forming of the stator, is filled at the time of a shrink fitting process.